/*
 * Copyright 2014, gRPC Authors All rights reserved.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package io.grpc.protobuf.nano;

import static com.google.common.base.Preconditions.checkNotNull;

import com.google.protobuf.nano.CodedInputByteBufferNano;
import com.google.protobuf.nano.MessageNano;
import io.grpc.MethodDescriptor.Marshaller;
import io.grpc.Status;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;

/**
 * Utility methods for using nano proto with grpc.
 */
public class NanoUtils {

  private static final int BUF_SIZE = 8192;

  private NanoUtils() {}

  /** Adapt {@code parser} to a {@code Marshaller}. */
  public static <T extends MessageNano> Marshaller<T> marshaller(
      final MessageNanoFactory<T> factory) {
    return new Marshaller<T>() {
      @Override
      public InputStream stream(T value) {
        return new NanoProtoInputStream(value);
      }

      @Override
      public T parse(InputStream stream) {
        try {
          // TODO(simonma): Investigate whether we can do 0-copy here. 
          CodedInputByteBufferNano input =
              CodedInputByteBufferNano.newInstance(toByteArray(stream));
          input.setSizeLimit(Integer.MAX_VALUE);
          T message = factory.newInstance();
          message.mergeFrom(input);
          return message;
        } catch (IOException ipbe) {
          throw Status.INTERNAL.withDescription("Failed parsing nano proto message").withCause(ipbe)
              .asRuntimeException();
        }
      }
    };
  }

  // Copied from guava com.google.common.io.ByteStreams because its API is unstable (beta)
  private static byte[] toByteArray(InputStream in) throws IOException {
    ByteArrayOutputStream out = new ByteArrayOutputStream();
    copy(in, out);
    return out.toByteArray();
  }

  // Copied from guava com.google.common.io.ByteStreams because its API is unstable (beta)
  private static long copy(InputStream from, OutputStream to) throws IOException {
    checkNotNull(from);
    checkNotNull(to);
    byte[] buf = new byte[BUF_SIZE];
    long total = 0;
    while (true) {
      int r = from.read(buf);
      if (r == -1) {
        break;
      }
      to.write(buf, 0, r);
      total += r;
    }
    return total;
  }
}
